Secondary Treatment

Question 1

Objective

Answer 1

To remove the soluble organic matter that escapes primary treatment and to provide further removal of SS

Question 2

Principal

Answer 2

removal accomplished by biological processes in which microbes consume the organic impurities as food, converting them into CO2, water and energy for their own growth and reproduction

Question 3

Basic Requirements

Answer 3

The availability of many microorganisms.
Good contact of these organisms with organic material.
The availability of Oxygen
Maintenance of favourable environmental conditions (temperature, sufficient time, pH)

Question 4

Types

Answer 4

Trickling Filters
Activated Sludge
Oxidation Ponds
Rotating Biological Contactors (RBC)

Question 5

Rotating Biological Contactors (RBC)

Advantages and Disadvantages

Answer 5

Advantages: High effluent quality, high process stability, short contact periods due to large active area, low space requirement, silent process and low sludge protection

Disadvantages: Continuous electricity supply required, contact media not available at local market, high investment as well as maintenance and operation costs, must be protected against the elements, requires skilled labour